This invention relates to knocking control method and apparatus for an internal combustion engine, and particularly to a knocking control method and apparatus for an internal combustion engine which correct the ignition timing of the engine to thereby suppress knocking.
So far, combustion of a thin gas mixture or supercharging of suction air has been employed for improving the fuel economy or power per unit volume of cars.
However, when the engine of a car is operated in such a condition, knocking easily occurs and in some cases, the running performance of the car is deteriorated and the power of the engine is reduced, and in its turn the engine itself may be damaged. Therefore, in order to obviate these drawbacks, an ignition timing control apparatus is known in which knocking is detected and the ignition timing is suitably corrected to prevent continuation of the knocking.
This technique is disclosed, for example, in Japanese Patent KOKAI No. 58-144652 laid-open on Aug. 29, 1983 in which, when knocking occurs in the engine, the ignition timing is corrected according to the intensity of knocking and then all the cylinders are ignited equally at the corrected ignition timing. This control method does not solve, however, such a problem as caused by non-uniformity in combustion of fuel among the cylinders, that is, different knocking characteristics of the cylinders from each other due to differences in air-fuel ratio A/F, internal pressure and cylinder temperature among the cylinders. Thus, when knocking occurs only in a particular cylinder, the ignition timing of the other cylinders in which no knocking occurs is unnecessarily adjusted and as a result the overall power output of the engine is reduced. This is contrary to the original object.